Out of the blue, my faithfull old Hoover washer tripped the RCD on my consumer unit.

After reset, it'll stay untripped when the machine is powered on at the socket, but as soon as I turn the control to anything other than 'off' the RCD trips.

The strange thing is that I've left the washing machine unplugged and yet the RCD still tripped a couple more times, but seems to have settled now and been ok for a few hours.

So, two questions:-
1. Any idea why the RCD might be tripping when machine is not plugged in (I'm assuming it is the machine that is faulty)

2. Assuming the machine is faulty, anyone know where to start looking for what could be causing the imbalance? Don't want to invest in a new machine if this one could be fixed easily/cheaply.

Note that the ring main MCB is not tripping, just the RCD for all the downstairs breakers.

I have electrical knowledge and multimeters etc. Just seeking opionions on what might be most likely.

Thanks, as always, for sharing your knowledge and experience.